Note: Descriptions are shown in the official language in which they were submitted.
~ 11061
~-~,.5~347B
This inventiDn relates to a process for the pro-
ductiDn of vanadium carbide V2C. This invention alsb
relates to a process fDr the prDductiDn of vanadyl hy-
drate, VO(OH)2.xH20, which is used to produce vanadium
carbide by the method of this invention. In particular,
this invention relates tD a solvent extraction, stripp-
ing prDcess for the prDduction Df vanadyl hydrate which
is further reacted with carbon by the method Df this in-
ventlDn tD produce vanadium carbide. Vanadium carbide is
well knDwn in its use in the prDduction of steel.
In accordance with the present invention an iDnic
aqueDus vanadium solution, such as a water leach solu-
tiDn containing sodium metavanadate, derived from vana-
dium ores or cDncentrates, is~provided. To this water
leach solution sulfur diDxide, S02, and sulfuric acid,
H2S04, are added in amounts described in detail herein-
after. The solutiDn which contains vanadyl ion is then
solvent ex~racted with an organic sDlvent, described in
mDre detail hereinafter. The rich Drganic sDlvent
containing the vanadyl ion is then stripped with
ammonium hydroxide, NH~OH, causing the vanadyl iDn to
precipitate as vanadyl hydrate, VO(OH)2~XH20~ where x is
unknown, as the vanadyl ion is rem~ved frDm the solvent-
In accordance with the present invention, the vanadyl
hydrate is blended with carbon, pelletized, and dried in
the absence Df oxygen and then furnaced to form vanadium
carbide.
The method Df ~e inventiGn will becDme more clear
when cDnsidered together with the accDmpanying drawing
which is set fDrth as being merely illustrative of the
$~
~- s ~ 11061
47~ --
invention and is not intended to be limitative thereof
and wherein:
Figure 1 is a simplified flow diagram illustrating
an embDdiment of the method of the invention.
The water leach solution used in the practice of
this invention is typically derived from the conven-
tional processing of vanadium ores Dr concentrates, such
as the water leach solution from a roasted vanadium ore.
Typical vanadium processes are described in U. S. Patents
3,132,920; 3,132,390; and 3,320,024. It is preferable
that the water leach solution be a true solution to
avoid cDntamin~tion Df the prDduct and to ease process-
ing. It has been found that the present invention only
works for vanadium in an aque~us solution. Typically a
water leach solution is an ionic solution of sodium
metavanadate, NaV03, with minor amounts of chloride,
sulphate, phosphate~ and silicate salts of sodium,
calcium, potassium, magnesium,and Dther alkali and
alkaline earth metals, and other impurities usually found
in water leach solutions derived from the processing of
vanadium ores or cDncentrates. For the process of this
invention to work satisfactorily the vanadium must be in
solution, HDwever9 the vanadium in solution may exist
com~ined with other elements as an ionic species such as
a vanadate ion in an i~nic solution of sodium metavanadate.
The vanadium in solution may also be derived from alkali,
or ~lkaline earth salts ~f pyrovanadate, orthovanadate,
decavanadate, Dr any other soluble form of vanadium salts.
Particularly in the practice of this inventiDn, the
source of ~anadium is sodium metavanadate. The
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~ , ` 11061
7~3
concentration of sodium metavanadate in water is not
critical and any concentration is satisf~ctory in the
practi~e of this inven~ion 85 long as the sodium
metavanadate is in solution. While there is no
preferred concentration for the sodium metavanadate in
solution it may be desirable at times in order to save
processing expenses to use as high a concentratiDn as
possible. Sulfur dioxide and sulfuric acid are then
added tD the water leach soluti~n. Preferably, the
sulfur dioxide is added first and then the sulfuric acid
in order to avoid precipitation Df vanadium as ~sodium
hexavan~date if the sulfuric acid is added first. The
sulfur dioxide is added in a sufficient quantity to
reduce the vanad;um ion in solutiDn from V+5 to V
valence. Enough sulfuric acid is then added to obtain
a pH in the range frDm about 1.0 to about 3.0, preferably
about 1.5 to about 3,0, ~nd more preferably abDut 2.0,
to obtain an optimum pH fDr solvent extractiDn whose
efficiency is sensitive to the pH. In ~ cDntinuous pro-
cess the sulfur di~xide and the sulfuric acid can be
added simultaneously tD ~he water leach solutiDn. While
sulfuric acid is the preferable acid tD use, other nDn-
oxidizing acids such as hydrochloric acid may be used.
Nitric acid should not be used since it is an oxidi~ing
acid. Acetic acid shDuld not be used since it is not
strong enough. PhDsphoric acid should also nDt be used
since it contaminates the product. The V+5 to Vt4 re-
ducti~n is measured by e,m,f. potential. ~he V+5 to
V~4 reduction is cDnsidered cDmplete when the optlmum
e.m.f. pDtential obtained is abDut -200 millivolts at a
4.
, , .
; ; 11061
~,5i~,r, ~7~3
pH2. An e~m.f. potential in the range of fro~ about -150
to about -300 millivolts is also cDnsidered satisfactDry
ln the practice of this inventiDn. V+5 exists in the
metavanadate ion, V03, and V~4 exists in the vanadyl ion,
V0 2. The concentratiDn of sulfuric acid is not critical
and can be added in any concentration but a higher con-
centration is desirable in order to avoid dilution of the
solution. The sulfur dioxide is preferably added as
sulfur diDxide gas but it can also be added in the form
Df sulfurDus acid or as a sulphite salt.
The acidified and reduced solution cDntaining vana-
dyl ion is now solvent extracted, preferably, in at least
a two stage countercurrent solvent extractor. The solvent
extraction step will becDme more clear when considered
along with the illustration of Figure 1. The acidified
and reduced solution containing the vanadyl ion 1 enters
stirred mixer tank 14 Df Stage I of the countercurrent
extraction step and is mixed with the organic phase stream
2 from settler tank 17 D Stage II. Mixed liquid 3 from
mixer tank 14 overflows into settler tank 15 of Stage I
with the organic phase 5 rising to the top and the aqueDus
phase 4 to the bottom of settler tank 15. The rich
Drganic solvent phase 5 of settler tank 15 is sent as
stream 6 to further processing described hereinafter.
The aqueous phase 4 Df settler tank 15 is then transferred
as stream 7 tD mixer tank 16 of Stage II wherein it is
mixed with lean organic solvent 9 and sulfuric acid 10.
l~e mixed liquid 8 overflows mixer tank 16 i~tD settler
~ank 17 wherein the organic phase 12 rises to the top 3f
settler tank 17 and the aqueous phase 11 settles to the
,, ! 11061
bottDm of settler tank 17. The aqueous phase 11 which
is the raffinate, also called tails, is discarded as
waste 13. The organic phase 12 of settler tank 17 is
sent to mixer tank 14 as stream 2. While the two stage
countercurrent extract~on step has been shown in Figure 1
in a simplified fashion more sophisticated equipment may
be used including more than two stages without departing
fr~m the scope of this invention. One stage may be used
but this is not deemed to be as effective as at least
tWD countercurrent extraction stages. It is conceivable
that a cocurrent extraction step may be used but that
would also be less effective than a countercurrent
extraction stepO The solvent extraction step is a puri-
fication step in the process ~f this invention.
Because the solvent extraction step consumes acid,
sulfuric acid or other non-oxidizing ~cid is added to the
Stage II mixer tank 16 to control the pH at an optimum
level of from about 2.5 to about 3, preferably from about
1.5 to about 3.5 in Drder ~o obtain the most efficient
extraction of the van~dyl ion by the organic sDlvent.
The preferred organic solvent fDr use in the extrac-
tion step is di-2-ethyl hexyl phosphoric acid as a 10%
solution by volume. In addition the solvent solution
contains 3% by volume of isodecanol (isodecyl-alcohol),
and 87% by -~lume of kerosene as a diluant. The di-2-
ethyl hexyl phosphDric acid does the actual extracting
of vanadium from the aqueous sDlution by complexing with
it. The isodecansl helps keep the vanadium ~omplex in
solution. Other sDlvents have n~t been used but it is
very conceivable that others will work such as hepta-
~ ~ 11061
~ 47 ~
decyl-phosphoric acid in mixture with lsodecanol and
kerosene. The volume percentages of the compDnents of
the organic solvent can be varied by those skilled in the
art withDut departing from the scope or purpose of the J
invention.
The rich organic solvent phase 5 cDntaining the
vanadyl ion is then sDlvent stripped and thickened. This
is ~ccomplished by first sending the rich organic solvent
phase as stream 6 to mixer tank 20 wherein it is mlxed
with ammDnium hydroxide 21 and a recycle stream 22 con-
taining recycled aqueous solution 23 from settler-
thickener tank 24 and aqueous filtrate 25 from filter 26.
It is deemed novel to use ammonium hydroxide tD strip
vanadium from the solvent by chemically reacting with the
solvent to form the ammonium salt Df di-2-ethyl hexyl
phosphoric acid, thus regenerating the solven~.
Sufficient excess ammonium hydroxide is added to mixer
tank 20 to strip the vanadium from the solven~. In the
previsus extraction step ammonium iDn is exchanged for
vanadyl ion, while in the stripping step the vanadyl ion
is replaced with the ammDnium ion. In the stripping step
the vanadyl iDn precipitates as vanadyl hydrate,
VO(OH)2.xH20, where x is unknown, as vanadyl iDn is
remDved from the solventO
The stripped mixture 27 fr~m mixer tank 20 overflows
into se~ler-thickener tank 24, wherein three phases fDrm,
an organic phase 28 on top CQmprising lean sslvent which
is sent to extraction Stage II as stream 9, below the
organic phase 28 an aqueous solution phase 29 which
contains excess ammonium hydroxide which is then combined
1 106 1
~50~7~
with aqueous filtrate 25 frDm filter 26 and sent as
stream 22 to mixer tank 20 combined with ammonium hy-
droxide 21; and a solid phase 30 comprising vanadyl hy-
drate which settles to the bottom Df settler thickener
tank 24, which is sent as stream 31 to filter 26. It is
novel and unexpected that three phases form in settler
thickener tank 24 and alsD that vanadyl hydrate
separates out gs a third phase rather than as an emulsion.
The filtrate 25 from filter 26 is cDmbined with the
aqueDus solution stream 23 from settler-thickener tank
24 and recycled as descr~bed above.
Filtered wet solid vanadyl hydrate 32 is blended in
blender 33 with carbon 34 and ~hen pelletized in
pelletizer 35, dried in dryer 36 in the absence Df oxygen
Dr air, and then furnaced in furnace 37 under vacuum Dr
inert atmosphere t~ furm vanadium carbide, V2C sh~wn as
stream 38 in Figure 1. It is deemed novel to reduce
vanadyl hydrate with carbon to prDduce vanzdium carbide.
In the past, vanadium carbide was produced from carbon
and vanadium trioxide, V203.
The invention will become more clear when considered
together with the follDwing example which is set forth as
being merely illustrative of the inventi~n and which is
not intended9 in any ~anner, tD be limitative thereof.
Unless utherwise indicated, all parts and percentages are
by weight~
8-
11051
5~7 8
EXAMPLE
The sample treated consisted Df 2097 liters of
water leach solution prDduced frDm a vanadium ore that
had been roasted with salt (NaCl). The solution assayed
4.05 grams V205 per liter, 27 grams Cl per liter and 7.8
grams S0~ per liter. The solution was acidified and
reduced using ~.91 grams S02 per gram V25 and 0.90 gram
HCl per gram V205. The variations in the pH and emf were
1.8 to 2.4 and ~190 to -160 mv. respectively.
This solution was processed by solvent extraction
ir. a two stage mixer-settler apparatus at a nominal flow-
rate Df one liter per minute. The raffinate averaged
0.04g V205/L resulting in a recovery of 99 percent of the
vanadium. The s~lvent was composed of 8% di-2 ethyl-
hexyl phosphoric acid, 3% Isodecanol, and 89% kerosene
by volume. The vandium enriched sDlvent contained 7.1
g V20s/L. The rich solvent was stripped by contacting
with 120 g NH40H per liter solution in a mixer then
separated intD three phases in a settler-thickener tank.
The barren solvent was recycled to the extraction
circuit. The aqueous solution phase was recDnstituted
with concentrated ~40H to provide stripping solution.
The solid vanadyl hydrate slurry was removed from the
the settler-thickener tank as a slurry, filtered and
collected as a wet filter cake. A sample of this
product (dried at 130 C) assayed 91.0% V205, 0.53~/0 S,
.
9.
- 11061
~ 7 8
0-21% Fe2~ 0.01% SiO2 and 0.022% P.
A portion of the wet filter cake was mixed with
powdered carbon and pDwdered iron using a ratio of 3.27
parts V20s to one part carbon and sufficient iron powder
to result in about 2% Fe in the final product. Iron is
commonly added as a densifying agent in the production of
vanadium carbide but is not necessary in the practice of
this invention. This mixture was formed into pellets
about Dne centimeter in dianleter which were then dried
and reduced to vanadium carbide in an induction furnace
under an argon atmosphere at 1700 C. The product
assayed 85.45% V, 9.99% C, 0.57% 0 and 0.002% N. This
product is vanadium carbide ~V2C).
Although the present invention has been described
and set forth in some detail, it should be further
understood that the same is susceptable Df changes,
msdifications and variations with~ut departing from the
scope and spirit of the invention.
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